The waters receded long after all life was gone.
It may seem like I'm trying to argue against a unified theory of what took place during the flood. I'm not really trying to argue something specifically related to that. I don't see a hot water/rocks situation here. Even so, I can't totally rule that out.
From the description of the way the bodies were grouped, it appears these creatures didn't die from hot water or rocks with water at depth.
If these creatures had died under that scenario, it would seem they would have been disbursed by normal currents and water flow.
These creatures seem to be grouped in a setting looking more like a natural large pod that was frozen in place. IMO, that comes from water receding, perhaps rather rapidly, as if the land was pushed up before the creatures could disburse.
You may have an explanation for this that would involve hot water or rocks. At this point, I don't see one.